How low does the gauge needle go before you run out

The Seicento ran out way before the needle was on the bottom red marker. My (T)rusty MG Metro would run below that no bother!

I've had my needle go all the way to the bottom.
The most i've been able to fill in is 34 l.

Cheers Santa, confirms what I've been thinking, as I get 25l in from when the light comes on, though I am reluctant to let my MJ get to low as I don't what all the crap and water pulled through the system.